Alex Simotas, MD

Hospital for Special Surgery
Board Certified Physiatrist
Specializing In Spine & Sports Medicine

Home > Conditions > Spine > Spondylolisthesis


Spondylolisthesis is the anterior or forward displacement of one vertebra in relation to the vertebrae below. The term spondylolisthesis comes from the Greek spondylos or vertebra and olisthesis which means “a slip”. The resulting positioning of the vertebra looks like a small step in the alignment of the spine.

There Are Two Types of Spondylolisthesis: Isthmic and Degenerative

Spondylolisthesis is extremely common and present in at least 15% of the population. The two most common types of this problem are called degenerative and isthmic.

The isthmic type of spondylolisthesis is associated with a weakness or true “crack” in the back of the vertebrae called a spondylolysis. Generally this develops in childhood or youth and can also be attributed to overuse injuries in adolescent athletes.

Degenerative spondylolisthesis is caused by age-related factors, and gradually develops in older adults. It may become apparent on xrays before it is felt to truly cause symptoms by age 30 or 40.

ISTHMIC SPONDYLOLISTHESIS: The Type with the “Crack” or “Spondylolysis”


Spondylolysis refers to a small crack that forms in the back (or posterior) part of the vertebra. The crack or break is called a lysis lesion. “Lysis”, from Greek, means crack or separation. A spondylolysis refers to this small fracture.

The exact location of the “lysis” is a small section of the vertebra called the pars interarticularis or simply “pars”. Approximately 5% to 7% of the population has a spondylolysis. There appears to be many factors that contribute to formation of a spondylolysis. Most of these factors appear to be genetically determined.

Adolescent Spine and Spondylolysis

Some cases of spondylolysis appear to be caused, at least in part, to repetitive stresses that occur in adolescent sports and athletic activities. The “lysis” develops gradually with repetitive stress to the bone, and not with one sudden injury. Therefore a spondylolysis is often referred to as a stress fracture in the spine. Certain sports that may produce a lot of stress loading to the posterior part of the spine are more at risk than others. Examples are gymnastics and American football.
The separation in the vertebra that exists with a spondylolysis may allow some forward slip or spondylolisthesis to occur. The amount of displacement forward one vertebra on the other is graded on a scale of 0-5. Fortunately the severity of the spondylolisthesis is established by adulthood and will generally not progress more than a degree after full growth. The severity again appears to be mostly genetically determined.

Grading the Severity of Spondylolisthesis

Spondylolysis will occur with two different types of spondylolisthesis: low grade and high grade. The severity of the grade is determined by how much of a step or “listhesis” is present.

Low-grade spondylolisthesis includes grades 0-2 is far more common. High-grade spondylolisthesis, i.e. grades 3-5, appears to develop at an earlier age. Of some concern a high grade spondylolisthesis and can be associated a narrowing of the spinal canal (see spinal stenosis).

Roughly 80% of people with a spondylolisthesis due to spondylolysis will never have symptoms, and if the condition does become symptomatic, only 15 to 20% will ever need surgery.


When an adolescent or young adult complains of persistent back pain that interferes with participation in a favorite sport it may be an indication of the presence of spondylolysis. Left untreated, spondylolysis can develop into spondylolisthesis.


A spondylolysis can be detected on plain x-rays when an actual separation or fracture has occurred. Often the lesion is only detected as an area of stress on a MRI or bone scan. The degree of a spondylolisthesis is an important part of the initial assessment and this is also best determined on plain x-rays.


Today there are a number of highly effective nonsurgical treatments that are used to treat spondylolysis. When detected early on, the adolescent may be asked to where a brace for 3 to 6 months to help healing to occur. Healing can occur with or without the reunification of the lysis depending on the type of lesion and spinal alignment. Physical therapy will be suggested to strengthen of the spinal musculature that will assist in supporting the spine and core. Sports participation will be modified according to the patient’s symptoms.

Almost all adolescents with spondylolysis will respond to nonoperative treatment. Effective surgical options are also available, when indicated.

Many different surgical approaches have been developed for spondylolysis and spondylolisthesis conditions. A direct repair means the surgeon will attempt to reunite (or fuse) the separate pieces of the lysis or crack. This is only possible in select cases with a small degree of spondylolisthesis.
Often a fusion of two adjacent vertebrae is necessary to assure a successful surgical outcome.



Degenerative spondylolisthesis develops as process of age-related degenerative spinal disease. (Age-related, and wear and tear changes of the spine are referred to as spondylosis). Women are significantly more likely to develop this than men.

The primary cause is a gradual aging change of the spinal facet joint and its supporting ligaments. The facet joint is the supportive and connecting structure in the back of the spine. Arthritic changes of the facet joints and ligaments gradually result in a low-grade spondylolisthesis. The arthritic changes and spondylolisthesis can lead to a narrowing of the spinal canal which is referred to as spinal stenosis.


Degenerative spondylolisthesis can be a cause of low back pain and sciatic pain (pain down the leg). In earlier stages it may lead to problems of recurrent back pain.

Degenerative spondylolisthesis in later stages can lead to spinal stenosis. In spinal stenosis the nerves that extend to the legs may suffer with poor blood supply that contributes to symptoms of leg pains, numbness and weakness.


Degenerative spondylolisthesis is detected on plain x-rays. The severity of additional problems associated with degenerative spondylolisthesis are best evaluated on a MRI scan. These problems include the extent of facet joint arthritis, the formation of facet joint cysts, and the development of spinal canal stenosis.


Treatment usually involves multidimensional therapies, which include oral medications, physical therapies, exercise treatment, and injection treatments. Anti-inflammatory medications can be effective however they need to be controlled because chronic usage on anti-inflammatories in the aging adult population is associated with a high rate of GI ulcer, hypertension, or possible kidney dysfunction.

Injection therapies can be very effect when performed with fluoroscopic guidance. Injections performed under fluoroscopic imaging help ensure the optimal delivery of medication to the targeted area. Injection therapies may include a facet joint injection, and a facet cyst aspiration. When a cyst is present, a joint rupture can be performed by injection as well. Some patients with persistent low back pain may benefit from a radiofrequency denervation procedure. Epidural steroid injections can be extremely effective if spinal canal stenosis and sciatica are present.

Surgery is recommended in select cases when a nonoperative treatment is not effective. If the severity of spinal stenosis (canal narrowing) becomes severe, and there persistent symptoms including pain, weakness and numbness, surgery may become the preferred treatment choice.